What’s the Difference Between Alternating and Direct Current

In electronics, you’ll be dealing with two types of electricity: Direct Current (DC) and Alternating Current (AC).

If you’re a beginner, you’re probably familiar with AC as the primary form of power distributed in homes and industries, while DC is predominantly utilized for low-voltage applications. These are all true, but what really is the difference between the two? Let’s find out!

What is Current?

Electric current refers to the flow or movement of electric charge in a conductor and is measured in amperes (A).

The direction of Current:

• Conventional Flow: Historically, it was assumed that electric current flows from the positive terminal to the negative terminal, known as conventional current flow. This convention is still used in circuit analysis.
• Electron Flow: In reality, electrons move from the negative terminal to the positive terminal. This is known as electron flow and is the actual movement of charged particles.

Alternating Current

Alternating Current or AC, is an electrical current that reverses the direction of the flow of electric charge at regular intervals. It doesn’t flow in a straight line like DC; it sways back and forth. This makes electrons switch directions regularly and creates a continuous oscillation.

We can represent the alternating current in a sinusoidal waveform. As you can see in the figure below, it showcases a smooth, repetitive oscillation over time.

Notice that the waveform oscillates around a central axis, known as the zero-voltage line. This line represents the point where the voltage is zero (where the current is also zero), and the waveform alternates between positive and negative values.

The highest points on the waveform, both in the positive and negative direction, are called the peaks.

Period and Frequency

The AC waveform completes one full cycle when it goes from its starting point, reaches a peak in one direction, comes back to the starting point, reaches a peak in the opposite direction, and returns. The time it takes to complete this cycle is referred to as the period.

On the other hand, the frequency is the number of cycles it completes in one second. It’s measured in Hertz (Hz). It determines how quickly the waveform oscillates; higher frequency means more cycles in the same time duration.

How is AC Generated?

Now, Alternating Current doesn’t just appear magically; it’s generated using devices like alternators and generators. These machines harness the principles of electromagnetic induction to kick-start the flow of electrons.

AC Applications

Generally, AC is the standard choice for power distribution in electrical grids. That is because it can be transmitted over long distances, with minimal energy loss during transmission.

Also, you’re likely aware that it is commonly used to supply electricity for lighting, heating, air conditioning, appliances, and various electronic devices. These the some of alternating current’s applications but we’ll not delve into it for now.

Direct Current

Direct Current (DC) is characterized by the consistent flow of electric charge in a single, unidirectional path. In contrast to Alternating Current (AC), where the flow of electric charge periodically changes in direction, DC maintains a constant and steady flow.

DC Applications

Many electronic devices, such as smartphones, laptops, and digital cameras, operate on DC power.

DC is also mainly employed in low-powered circuits, especially in digital electronics. For example, if you’re working with integrated circuits (IC), microcontrollers, and LEDs, you certainly need DC power to make them operate and function properly.

If you’re new to electronics, it’s generally recommended to start with Direct Current before delving into AC. It is simpler to understand and work with initially. The concepts of voltage, current, and resistance are straightforward in DC circuits.

DC Sources

• Batteries can used as compact and portable sources of DC power. They generate electric current through chemical reactions, providing a reliable and steady supply for various applications.
• Solar cells, or photovoltaic cells convert sunlight directly into DC. These cells generate a voltage when exposed to light, and multiple cells can be connected to form a solar panel.
• DC Power Supply convert electrical energy from outlets into a stable DC output. If you’re a university student or a hobbyist, you probably have access to a DC power supply.

Alternating Current to Direct Current

Speaking of power supplies, DC can be produced from AC through a process called “rectification.” It involves converting the alternating direction of current into a unidirectional flow. There’s a separate discussion to it, but to give you an idea, the key component relies upon a rectifier circuit. When AC voltage is applied to this rectifier, it forces the current to flow in one direction only.

To wrap it up, note that each type of current has its strengths and is better suited for specific applications. If you’re designing and working with circuits, you should know how to generate these types of current.